If you use a Windows PC, create a text file containing:
.LOG
as its first line, and create a shortcut to open it in Notepad, placed wherever best suits your workflow. When you open it, Notepad adds a date/time stamp at the bottom of the file and positions the cursor below it ready for you to add new notes. When you close it you'll be asked if you wish to save or discard any changes, including the new timestamp.
If you are doing a lot of copy/pasting from your web browser or other documentation,
Microsoft Powertoys offers an 'Always on Top' function, which if enabled is activated by keying Win+Ctrl+T (unless you change that) while the window you want to keep on top is in focus. You can also automate setting a window always on top with various macro or scripting utilities, e.g. AutoIt 3 or AutoHotkey, if you want the window to be always on top automatically when first opened.