Preservation of existing switchgear

Hello,
I would like to use an existing built-in double-pole pulse wall switch as a “virtual” switch for controlling Homey flows. I think I can do this by placing a mini smart built-in switch behind the physical switch in the wall box. I then do not connect any wired lights or appliances to this switch to L-out. This means that the visible appearance of the existing switching material on the wall does not change.

My intention is to start a flow with the push of a button on the wall switch. Pressing the switch should then be seen by Homey as a state change, which I can then use to create a flow.

For example, if the last person leaves the room and that person can then start a flow with the push of a button, whereby all lighting is switched off.

I also have an unused sunshade switch on the wall (which are also 2 push buttons). I think that should also work.

Does anybody have experience with this?
Should this work like this?