Go on, spend £250 on the Festool CXS drill driver from Screwfix.
On the divorce present to self.
Drill the hole through the inside wall of the cupboard?
Not necessary, it’s got a hole in the back.
I think you are going to be frustrated by the length of the handle.
If it’s that tight already it’ll be even worse when you are trying to fit the blind with the blind in the way.
Have you considered glue of even quality velcro?
From the layout I’m pretty sure I can get the flexible drill snake thing in, don’t need the blind on the rails while I fit it, but the blind is held under tension when fitted so no way velcro would work, glue perhaps but more messy and still a good possibility of failure I reckon.