Reported on Meta.SE. Related report here.

Is your feature request related to a problem? Please describe.

Link editing and insertion is currently confusing. The button only highlights when text has already been selected and you cannot insert a link without pre-selecting text.

I’m not sure all users will understand how the ‘Link selection’ button works. (Hint: you have to select the text first, then the button will become enabled.)

Describe the solution you'd like

Other rich text editors I use regularly have an 'Insert Link' button where you can specify both the link and the text to display.
So something like this (excuse the bad mockup, hopefully the idea is clear):

Or enable the button at all times, and if nothing is selected, ask the user for a link (like the current editor) and insert it, with the popover visible so that users know they can edit both the link text and the link itself: