I block off some time each day to do ‘something technical’. Sometimes it’s making something pretty that was ugly before. Sometimes it’s learning a new tool my team is considering to pick up. Generally these are things that are important, but not urgent.
For larger projects, I often attend the design reviews. Sometimes I help on the designs, especially if it’s a new product altogether.
All managers on our team are also required to participate in the on-call rotation.
Between those three, I feel like I am still “in the trenches” enough to not forget what it’s like.
It's been 1.5 years since I transitioned from a Solution Architect role and into a Technical Manager role, and I still struggle to keep myself out of my devops-team's kitchen. I'll still offer advice and direction based upon my past experience, but try to maintain those "teachable moments."
But for me, the only way I could fully scratch that technical itch is to pick up some hobby electronics projects at home.
Ironically, most recently I ended up building an Arduino traffic signal light for the office, interpreting data from our Sensu/Telegraf/New Relic APIs, just to show my team when our servers are struggling. Heh
I have also seen some still be able to get into the nitty gritty too to help solve problems that are critical & beyond their reports' abilities at the time and to ease the pressure.
But you can certainly do something small in between.