We have the same need here:

For one of the documenttypes we maintain in TD the correct maintainance of the properties is essential for a downstream process, even although the properties are optional.

And also the writers teams of other documenttypes complain about the exisiting toggle: it's annoying to be forced to switch on the optional fields for each single session in Organize Space. 

Directly seeing them would really be helpful. An alternative could be to having an option for the user to set a toggle "always show optional fields"

Hello Julia,

Thank you for your question.
I am glad to say that there is a community idea that was recently reported for this case
Show optional fields in Properties activated by default
Please vote for it if it is relevant to you.
Some additional questions that I would like to ask:

• Should it be a system-wide setting or a per-user setting?
• What default would you expect, I assume "Show Optional fields" = true.
• How often from your experience might people change this setting or will it be set once and forever?

Please leave your comments on the community idea. 

Thank you

I voted for both instances of this idea:
Tridion 15: Allow for "Show optional fields" option to be enabled by default I am unhappy to see that this one is marked "Not considering."
Show optional fields in Properties activated by default is the newer version of the same idea. It is also getting good traction but is marked "New." Hope springs eternal.

As for your questions:

• I would guess implementing it system-wide is easier. Per-user would also be acceptable if it's easy to find (we'll add it to the installation instructions and then everybody can forget about it again).
• I would expect the default Show optional fields = true
• I doubt most users would change it after it's set to true because in our process, many of the "optional" fields are functionally mandatory. Everyone grumbles about having to hit the toggle over and over, or having to go back and correct properties when someone forgot to turn the fields on and fill them in.