There are 4 basic ways to adjust the height of the router bit.
1. The router is mounted in a large extension without a plate, so you have to reach under, release the lock, raise or lower it and measure or run a test scrap.
2. The router is mounted to a separate plate that has various size adaptors for different diameter bits. You can pop the plate up on the table, measure the height and drop it back down and run a test scrap.
3. You router has a built in height adjustment that will accept a wrench from the top side of the table/bottom side of the router when it's upside down. The router stays put while you adjust the height using the wrench.
4. The router is mounted to a lift mounted on a removable plate. The plate stays put while you use the wrench that came with the lift to adjust the height.
This is what I use and it saves time and is vary precise. Some earlier lifts (Jessem) did not have a height locking feature, (I have one) and were prone to changing heights during a run. The newer Jessem/Incras do have a locking cam and stays where you set them.
As far as I know the Benchdog extension comes with a "smaller plate opening" than most and will only accept the small size 8 1/4" plates. The Incra lift comes with a small size plate. I don't know without searching if Jessem still supplies their own like than.
A router lift may be a luxury to some, a necessity to others based on how much you use it........ They are expensive at $300.00 or more for the quality ones.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)