You can use a profile for this (General). Also use in conjunction with a timer to control the period within which you want to charge e.g. to take advantage of off peak charging times.
Before all of that download the Porsche Good To Know App and review the charging sections and videos - all explained there.
Set general profile to 25% minimum charge. If you have time of use penalties you can set those here also.
Set timer to the time you want to get up, every day, and set 85% on it.
The car will now charge during your optimum charge window and stop at 85%.
Note that if you're ever below the 25% when you plug in, it will immediately charge to that level and ignore the time of use window.