I need this functionality as this is how I use my Outlook and Gmail. All emails sit in the inbox as unread if an action is needed. Once the action is done, then the email is manually marked as read to signify that I am done with it.

Some User,
what tags are you talking about.
Are you suggesting that we add new label "unread" and manually remove it when we read the email.

I'd still prefer to use mark read and unread with Proton offering an option to not assume I've read a long email with multiple attachments just because I previewed it.

Though thank you for sharing, I appreciate it

You can do that using tags. Or folders.
Create filter that adds the tag to all new emails,manually remove it when done.

I really need it for the reasons already mentioned by others.
I can work around it only if I use another mail client via proton bridge but that does not help on any other device.

Was surprised to see that it is not there as it is a basic thing. Should not be hard to just not do some action on mail open.
Really hope that it will be made possible.

Switching from Gmail now - and being very used to heavily utilizing this feature as well as it allows you to skim thru mail, know what it's about and mark it as read only once dealt with. Exactly, a to-do list. Otherwise, I would need to remember which emails to get back to... and I hate remembering stuff because of information overload plus receiving so many unimportant emails..

please lord

For me, this kind of function is standard, so I was surprised that it wasn't there. Please fix this urgently.

Yes, exactly.
I need to skim through the requests first and
estimate the processing effort,
but only mark them as read once all the requested information has been retrieved.
Otherwise, the requests will get lost in the flood of emails.
Thunderbird and many other email programs can do this.