If you want the functionality inside Signal, then only the Signsl devs will be able to help you. If you want a solution outside from that, look into desktop env

If you want the functionality inside Signal, then only the Signsl devs will be able to help you. If you want a solution outside from that, look into desktop environments that have a feature to lock a specific app. Or use multiple accounts. That is what it's designed for I would say.