Correct on the if I just want to check the doors are closing post - you can not do it without a Certificate of Approval, complete jacking needs to also be in a hangar.
What you can do and have done is jack a 210 so the nose wheel is just touching the ground. Remove both main gear actuators carry out service bulletin inspections and modifications on them and install them ( a visit from CAsA was expected and they did when I was not there - they saw a 210 with no main gears, we had lowered it to a lower position) then get a job number for a job from a CofA holder with a remote location attached to the approval (and all reqd manuals), to fully jack and do retractions.
All 100% legal - you will find most maintenance done under schedule 8 is not legally done, from manuals, tooling required, documentation retention and parts. All CAsA regulations and requirements apply as if they were a LAME working for a company that has a CofA carrying out that list of tasks.