I have extruded alum T slot bars on several pieces of equipment.
Search for "T-Slot nuts".
They make drop in T-nuts that have a set screw to lock them in position (what I use most). I've have some with lock balls
The ones that drop in and rotate 90 degrees hold well, but sometimes are a PITA to get them to grab.
There are some super cheap "double" bolt nuts/bars, that are probably the most secure but are made of steel and would be prone to rust and just about have to be siliconed in place in order for the bolts to be removed and replaced. Once they are slid in the T slot with a bolt installed, easy........... but once the bolts are removed, the nut drops down and is dang near impossible to line up and put the bolts back in. The solution is to position and secure whatever, then squirt some RTV (silicone) under the nut bar which will hold the nut in place when the bolts are removed.