Programming

That's a very one-dimensional view of technical debt.

I was about to write something more, but I think if I don't know what they refer to when they say "knowledge", then it's too wishy-washy and I may be talking about something different than they intended.

Contrasting “resolving technical debt” and “investing [improvement] knowledge” we're moving the reference view point.

I document state and issues as technical debt, and opportunities for change as opportunities. They cross, but are distinct concepts, and do not always cross. Some technical debt may be documented without a documented opportunity. Opportunities may be open improvements that do not tackle technical debt.

In my eyes, technical debt is about burdens that reduce maintainability where better alternatives likely exist.

"Investing knowledge" is something different, and not necessarily about known burdens, but may be improvements unrelated to known burdens.