Flex/Follow Tempo On/Off ⌃F
Changes the “Flex & Follow” setting for the current region. Choices are Off, On, On+Align Bars, and On+Align Bars and Beats.
This allows you to adapt notes/transients to fit into bars and beats by changing the tempo accordingly.
Overview of Flex Time and Pitch in Logic Pro – Apple Support
You can configure how Flex Time and Follow Tempo adjust each region on a flex-enabled track using the Flex & Follow pop-up menu.
Logic Pro | F is For Flex and Feel:
Finding the right feel for our music is an incredibly important part of getting it to sound right. Fortunately, Logic has a lot of tools to help us control, correct, and capture the feel of our performances. Among the tools in our toolbox are Fex Time, and the ability to make custom groove templates.