ND3 2024. When I originally fitted my Nextbase dashcam using the hardwire kit, I simply inserted the fuse holder supplied with the kit into a spare slot in the fusebox that had permanent live so that the camera would record even when the ignition was switched off. Subsequently, I have found that the 422GW has a parking mode and hardwiring it to a permanent live is unnecessary. The piggyback fuse holder supplied by Nextbase will accommodate two fuses, the NB one for the dashcam and the original Mazda one (the slot I intend to use). However, the standard mini fuses are different from the NB (see photo below) one in that the prongs on the standard fuse are shorter, the middle plastic bit stops it being inserted into the piggyback holder. My question is, can I just use a standard mini fuse in the piggyback holder in place of the shorter Mazda fuse, providing it is of the same rating of course? I was thinking of using the 15A audio fuse slot because this should only operate when the start button is pressed (I think) or would another slot be preferable? The blue fuse on the left in the lid is the Mazda 15A fuse, the clear one on the right is the NB one 2A I think for comparison.
I think it’s still best to have a permanent live connection, and have Smart Parking enabled. According to these links the dash cam goes into standby after 5 minutes of no physical movement, and wakes to record if there is an impact. It will then decide to use either built-in battery power if there’s enough, or car battery power if not. Then it goes back to sleep after another 5 minutes.
Thank you so much for your reply, really helpful. I have checked the settings and the auto power off/screen saver wasn’t enabled, neither was parking mode. No wonder the thing was staying on permanently unless I pressed the on/off button on the side, Doh!
I do have an excuse though, I only installed it 2 years ago. 
No need to wire it into that fuse board, use the one bottom of the A pillar in the passenger footwell, I did but mine turns on/off with the ignition.
TBH, I wasn’t even aware there was another fuse board inside the cabin until much later on! I just opened the bonnet, opened the main fuse box & selected a spare slot. In fact, with the roof down it was relatively straightforward to feed the cable into the engine bay without having to route it through the bulkhead somewhere which I might have had to have done with a fixed roof car. Every day is a school day I suppose!
In addition, there is a small black box incorporated in the hard wire kit which has a tiny blue light which indicates the dashcam status. It would be difficult to mount that in the cabin discretely, easier to mount it in the engine bay.