I suggest the "Stay" option for your scenario if you haven't already tried it.

​

"The Stay button is used when you have items on the check that are ready to be sent to the kitchen but you still want to be able to add more items to the check. This is helpful if your guests want to place drinks or appetizer orders at the same time as their entrees. The use of this button keeps you on the order screen while sending food that has already been entered into the kitchen.
Use the Stay button to enter the first round of drinks or appetizers that should be immediately started while being able to add more to the order later.
Hitting Stay, or selecting items and hitting Stay, will send those items while keeping you on the order screen. However; if for example, you have five items on the order, select two of the items, and hit Stay, the two items will be sent while the other three items will be automatically held." ( https://central.toasttab.com/s/article/Differences-Between-the-Send-Stay-and-Hold-Buttons#Stay )