In a roundabout way, perhaps. Move the code you don't want to debug into a unit (or units), disable all debug info, then compile with -Ur option. Then move unit source and compiled unit (.o and .ppu) to a separate folder (this may not be necessary, but in my case it avoids confusion), add this folder to the project (or compiler command line using -Fu).
Now a debugger will not find debug info for the compiled unit, and Lazarus will not try to recompile the unit to add back the debug info (which you obviously want to add to your project).
This way you can still "step into instruction" when in assembler view, but normal F7 should step over a function call into this unit.