Modular corner bracket, for Ultimate Cereal Filament Drybox

I created this modular holder for GunplaMark's Ultimate Cereal Filament Drybox, because I never liked the hygrometer hanging on top of the filament exit port (unstable angle against gravity). Instead, this mod allows to put some accessories in a stable manner inside the drybox, This adds 2 connectors to the internal corner bracket, allowing to place plug-ins (such as hygrometers) directly underneath each bracket. Currently, there are 3 plug-ins to choose from: Square digital humidity sensor adapter. Round digital humidity sensor adapter. Analog humidity sensor adapter (these can be found cheaply on aliexpress, and require no batteries). That makes those dryboxes look so much neater and polished! In addition to those modular connectors, this version supports using heat inserts instead of nuts. I found the original corner bracket for the Ultimate cereal drybox by GunplaMark too difficult to install because of the M3 nuts so frustrating to mount. Then I discovered zktec_3322325 's remix that replaced the nut cavities with holes to accomodate threaded heat inserts, and it proved much easier to assemble than the original. So I kept that feature for the bracket here too.