I just saw those for automotive use on Amazon...completed a room build out at my house and used the Wago ones for home wiring for the first time and I love them! Totally sold on them. For automotive I think if you packed with dielectric and then used a good electrical tape over them would handle anything except full submersion...so should be safe up at the upfitters. But honestly need to try it and see how well it works.When I worked for a company making military shelters, we started using these. They can take a wide range of wires and clamping force is very high, so the wires don't pull out. They are not water tight as far as I can tell, but super easy to use and can move wires very easy. Come in different terminal lengths as well (3, 4, 5). I don't know how these would hold up under the hood of a truck though...
https://www.digikey.com/en/products/detail/wago-corporation/222-412/VE00-2500/13549446?utm_adgroup=Terminals - Wire Splice Connectors&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Product_Connectors, Interconnects_NEW&utm_term=&utm_content=Terminals - Wire Splice Connectors&gclid=CjwKCAjwy7CKBhBMEiwA0Eb7aoQRFbjoHEffhYUy3VKDaPvRGmRnBc_F2i25R6Sz3-hZ_zRvOZLwjBoC3ToQAvD_BwE