I noticed on a SharePoint wiki library that the bookmark functionality was disabled. When I hovered over the textbox for the control it provided the following prompt:
“This control is currently disabled. You might not have the right permission level to use this, you might need to select an object or item, or the control might not work in this context.”
I had used this functionality on other sites, and was puzzled why it was disabled in this instance. The answer, luckily, ended up being simple. The “Bookmark” functionality as part of creating links is apparently dependent on the site collection feature: SharePoint Server Publishing Infrastructure.
It is also dependent on the SharePoint Server Publishing site feature:
Once these features are enabled on the target site, then the control is also enabled: