Q: Should I write to the editor if the status has been 'Decision in Progress' for 20 days?
Under normal circumstances, 20 days may be considered a relatively long time for a decision on the manuscript. Sometimes, though, there may be a lot of manuscripts that the Editor-in-Chief (EiC) has to decide on. Presently, COVID-19 may be presenting an additional challenge, going by this other query: Could COVID-19 be affecting how long my manuscript remains in the 'Decision in Process' status? As is understandable, there is a surge of manuscripts being submitted around various aspects of the disease, and journals may be prioritizing these over other manuscripts (unless yours too is related to COVID-19).
However, it’s also understandable that you should know the fate of your manuscript soon enough to be able to make decisions of your own. So, you could wait for a few days more, say, till a month gets over, and then write to the editor requesting an update. All the best for whatever’s next!
For more insights on the ‘Decision in Process (Progress)’ status, you may refer to the following resources: