I was facing same problem and it worked when I used Light Mode instead of dark mode.
Steps I followed are
1. Make sure both devices ( Galaxy Tab and Galaxy Phone) are on same wifi network and band ( example 5 Ghz)
2. In bluetooth settings of Galaxy phone pair Galaxy Tab
3. Use light mode in Tab's display setting ( not working in Dark mode)
4. Open Samsung Notes app in Galaxy Tab then click on 3 horizontal lines on left top corner then click settings and you will see "Use phone as toolbar" is no longer greyed out.
5. Go back and create new note and you will notice new Icon with an arrow on right top corner.