RC has a frustrating limitation:
When configuring phone hardware, Phone must be set up as EITHER a "User Phone" or a "Common Area Phone".
-The only way "hot desking" login is possible is to configure device as a "Common Area Phone".
-"Hot desking" login by other users is impossible on any "User Phone" devices.
-Fun fact: Every night any users signed into a "Common Area" type phone are forcibly logged out, necessitating the login process EVERY MORNING for the phone to work.

Consider this case:
'Employee A' works in a busy lobby 95% of the time.
Due to sickness or emergency, 'Employee B' or others are called upon to fill in at this desk 5% of the time.
'Employee A' NEEDS to be signed into this phone by default. This is their desk.

Presently the options are:
Option 1) Setup the phone as a "hot deskable" device or "Common Area Phone", but the login process INCONVINIENCES 'Employee A' every single morning, and often they forget to login at all.
Option 2) Tell 'Employee B' they will not be able to monitor their extension today while they fill in for 'A'. They don't like this. Yes, they can setup call forwarding for a day, but they is not the same as being signed into hardware.
Option 3) People physically move their phones around, I don't appreciate this as phones take time to boot up, and they can be forgotten and must be swapped back.

HOW IT SHOULD WORK:
All phones, even if the device is setup as a "User Phone" should have a "login" button on the main menu. This would allow any extension to sign in and takeover hardware for the day. The main user's Ext should be temporarily placed in an unavailable state (while they are not signed into any hardware at all). Manual logout or overnight reset should sign out temporary user, but leaving the phone ready and assigned to the main user.
This is how real flexible hot desking works.

Another example:
Imagine Users 'Rock', 'Paper', and 'Scissors' each have a dedicated phone. They expect to be signed into their phone by default every morning.
Lets say it is a crazy day, and due to unforseen staffing problems:
1) 'Rock' must takeover the physical workspace typically used by 'Scissors', but EXPECTS to bring his phone extension with him.
2) 'Paper' must takeover the physical workspace typically used by 'Rock', but EXPECTS to bring his phone extension with him.
3) 'Scissor' must takeover the physical workspace typically used by 'Paper', but EXPECTS to bring his phone extension with him.
Calls placed to Rock's extension (which was displaced from his typical hardware) SHOULD ring on the phone at Scissor's desk (since Rock is signed in). All these changes should be temporary, and tomorrow morning users should find their phones reset back to normal.

Regardless of where they find themselves, Each should be able to 'login' and commandeer the phone hardware for temporary use, regardless of its typical and permanent user. Typical and permanent user should find themselves still signed in when temporary hot desking session is over.

If permanent user's extension is 'displaced' due to another user occupying their phone hardware, extension should follow their "incoming call rule" skipping phone, and going to VM or forward.

I admit, I previously enjoyed this feature with a competitor's platform! Disappointed RC doesn't do this well