Glue Tool G
Using the Glue Tool saves an extra step when joining regions. When you join regions you select them and issue a Join command (command-J). With the Glue Tool selecting the regions joins them as you select.
Counterpart to Scissors Tool which will split regions everywhere you click.
You can choose the Glue Tool by selecting it from the Tool Menu, or, press T (tools) then G (glue).
I like using the T command to bring up the Tool Menu right at the location of the pointer. Handy.
Common Logic Pro tools – Apple Support
Use the Glue tool to join selected regions or events into a single region or event