Can you let us know what happens when you choose Edit→migrate previous local settings?
A message pops up telling me that InDesign needs to close and reopen to migrate [all?] settings from Indesign 2017.
I chose not to do this, since:
1. The update to Indesign 2018 kept all the old settings from 2017 EXCEPT user-created Workspaces.
2. I've already manually set up the old 2017 Workspace settings.
It would be helpful if InDesign 2018 migrated user-created workspaces as Photoshop 2018 does.