Alt+T, E is all you need to press when the LSP stops working in Delphi.
Delphi 12.3 introduced a new menu under Tools -> Reload LSP server. Alt+T, E is it keyboard accelerator.
It will require under a second for LSP to restart. However, the menu will not be available to be reused for quite a while after that (it will be grayed out).
I checked the PID. All three processes are restarted.