Pilot reported an inadvertent taxiway incursion at CXY airport after attempting to reposition an aircraft away from an uneven ramp area. After towing the aircraft to a level area; it was discovered that the aircraft was sitting on an active taxiway where a blind spot exists from the ATC tower's perspective.

Narrative

I entered a taxiway without permission. Taxiway J in front of the FBO. The available parking space in front of this hanger is limited. When arriving I pulled off the taxiway to the left side of the hanger. The ramp was full to the right side of the hanger; and I chose this spot so as to not block the entrance to the hanger which appeared to have another aircraft in the process of being towed out. This part of the ramp is in very poor condition with a dip of one to two feet over a short distance. When I was ready to depart for my return flight; I was concerned with the dip and the available distance to make a 180 turn. Someone helped me move my plane and towed it out onto the taxiway. I did not think about being in violation until I started the plane up and was ready to taxi. This part of the ramp is not visible to the Tower; so I was able to get taxi instructions without the Tower noting my position. I am making this report because a couple of months ago I had a similar incident on this airport. There is an area on this airport on Taxiway C which is also not visible to the Tower. This spot did not allow radio communication with the Tower; and I taxied past the line on the ramp where the taxiway officially starts without permission. This is also an area on CXY where the Tower cannot see the taxiway. As I reflect on how all this happened; I ask the basic question. Why are there taxiways on this airport which are not visible to the Tower? Both of these locations look and act like ramps to me. Neither taxiway goes anywhere except to a dead end. I would suggest that the entirety of both Taxiway C and Taxiway J be reclassified as ramp areas. While the Tower issues taxi instructions for these two taxiways; they cannot see most of them and pilots are responsible for taxi safety in those areas anyway. I would guess that if asked; the Tower Controllers would tell you that both taxiways are an unnecessary headache for them as they must issue the not visible warning constantly.