Second, make a backup.
Third, just download PenWindowManager_v1.apk - [Click for QR Code] and install as normal.
NOTE: If you have previously edited others.xml or features.xml, you may have introduced some errors to the xml file layout which would prevent this app from properly functioning. Editing the said xml files manually is not advisable due to human error of breaking the xml structure by accident. If this app does not work after previously manually editing the said xml files, then I suggest you restore the original unedited xml files.
For those who don't seem to have a /system/csc folder and either others.xml or features.xml files in said folder, then you may want to try a custom rom that includes it but if you want to try, you can create the csc folder and procure a copy of others.xml or features.xml and put it inside the csc folder.