Consider allowing the “Study” Action as a Bonus Action.
The Study Action (PHB ‘24 p.375) reads as follows:
“When you take the Study action, you make an Intelligence check to study your memory, a book, a clue, or another source of knowledge and call to mind an important piece of information about it.”
You spend your Action and make an Intelligence check; simple and easy. The issue is that, just like sipping potions as an Action in 2014 5e, it’s extremely unsatisfying, especially at higher tiers of play where a player’s Action becomes increasingly valuable. Players don’t know what kind of information will find before they take the Study Action or if they’ll even succeed at all, which makes it hard to justify compared to swinging a weapon, casting a spell, or any Action with more predictable advantages.
Consequently, consider making Study a Bonus Action instead. Having tested it over four sessions, I’ve found that it significantly increased the enjoyment of my more cerebral players (who could ask a question, roll for a possible answer, then spend their Action reacting to what they learned) while preserving the general Action economy. Having players asking questions during combat also gives me more opportunities to reveal details about the enemies and environment, which feels more organic than hamfisting them into lengthy combat descriptions and/or NPC banter. Give it a shot and see if it’s right for your group!
TL;DR: The Study Action feels terrible as an Action but great as a Bonus Action. Consider making Study a Bonus Action if you’d like your PCs to problem-solve during combat.