ChrisD any synchronization of that category group and the account will be on you. It's actually unnecessary to do so  (and additional effort). Read the following for more details:

https://www.youneedabudget.com/the-relationship-between-your-budget-your-accounts-its-complicated/

ChrisD certainly move excess money in your checking account into an account with a better interest rate. But don't think in your head that grocery money lives in my checking account, vacation money lives in my savings account etc. Location and purpose are 2 different things (look at the link dakinemaui posted). In my case I keep a maximum of $X in my checking account. Regardless of any of my category balances, anything over $X gets moved to a high yield savings account. I won't "accidentally" spend my Income Replacement fund on dinner and a movie because those expenses will be allocated to Restaurants and Entertainment categories respectively and I make my spending decisions based on category balance, not account balance. Now, let's say my credit card statement closes on September 27 and the bill is equal to $3X because I had a major expenditure that month. But if all my purchases were fully budgeted it's fine. The bill isn't due until October 20 and as long as I pay the full statement balance by then, there will be no interest charges so I have more than enough time to move money out of my savings account and back into checking in order for there to be enough money in the checking account on the day that it autopays the statement balance.

ChrisD As you use YNAB, you'll find money accumulating in categories other than that EF group -- money that can also earn additional interest.

Many experienced users base the movement to the higher rate account on cash flow: i.e., the estimated minimum account balance over the next month or so.  They keep enough to satisfy account minimums + a cushion for unexpected expenses not considered in their estimate, and the rest goes into savings. Their account balance therefore won't match the EF group, but that doesn't matter.

ChrisD If I may...there's a sliding scale between "one big emergency fund that in my imagination will cover everything I ever need even though it won't" and "so granular that I'm budgeting $6 a month for the dishwasher breaking." Most people budget somewhere in between. So if you find these small amounts make budgeting difficult, I would suggest bigger categories, perhaps "Auto maintenance" and "Home Maintenance" and "Medical." 

It's easier to focus on maintaining the right amount of money in the checking account, and just keeping anything else in the savings account. Most of the time you'll end up with a larger savings account and more earned interest.

ChrisD I could be misunderstanding, but it also sounds like you are trying to transfer those exact sinking amounts to your savings account every month.  That will get really confusing really fast, especially if you have a large bill that needs to be paid from your checking account.  Just do as nolesrule said, and keep an eye on your checking account, transfer extra to savings for the interest as appropriate, and let the budget categories do the rest of the work.

ChrisD What's the point of building up the EF only to invest most of it and replenish? Time in market is the key, so if you want to invest your EF, take some of what you are putting toward the EF now and invest monthly or quarterly.

Not that I'd recommend that. What I would recommend is getting your categories where you want them to be and keep them there. Then invest any money you don't need in your budget.

Why don't I recommend investing the EF? Because you should not invest money you might need in less than 5 years (and preferably 10 years). An EF is what I like to call Schrödinger's Category". It has a time horizon that is both infinite and immediate at the same time, but you won't know which one until you need it. As such, one should err on the side of caution.

ChrisD I'm detail oriented too. The trick is too adjust where you keep the details. I use Google Sheets to keep calculations outside of YNAB.

For example, I use the save 1% of the value of your home for home maintenance and repairs rule of thumb, since my last home was not all that old, and my current one is 8 days old. I actually save 1.2% of the value, since I budget 0.1% per month (keeps the math clean). However I also differentiate between home maintenance, require costs, and home improvement, which are wanted upgrades.

When we sold the old house last month, I had 18 months worth of funds in home maintenance, even though we'd lived there for 5 years. Some of it gets spent monthly, some on capital costs. We had replace almost all of our appliances in the last 2 years because they had reached EOL.

ChrisD Folks are big fans of simplifying around here! 😉 We recommend keeping the structure simple, because it keeps your financial life simpler, and leaves more time for you to focus on your priorities. 

Check out our Simplify Guide, for more on that. Detail can be great in certain places. Ultimately, you'll figure out what works best for your budget! And we're here to help talk through it.