Tied finger numbers (Elision)

Here's how I do it:
1) Add the two finger numbers (21 in this case) as usual.
2) Click the note, press CTRL+T (Add Staff Text), a text box appears.
3) Press SHIFT+F2 or click the “Insert Special Characters” button in the Properties panel.
4) In the Special Characters dialog, go to the second tab “Musical symbols”, choose the “Fingering” category in the list on the left and click on the “Finger substitution above” symbol (the third in the second row).
5) The symbol will be inserted. Close the dialog. Press ESC to leave text edit mode.
6) Using the arrow keys, move the symbol so that it is above the finger numbers.
7) In the Properties panel, increase the font size so that the symbol covers both finger numbers well and looks well. If necessary, move it further with the arrow keys to reposition it better.
That's it. :)
Note 1: you may want to send this symbol to the back (in the Properties panel) if it prevents you from editing the finger numbers or manipulate them in any other way if you need to.
Note 2: once you've done this once, you can CTRL+SHIFT+drag this symbol to a palette in order to skip steps 2, 3, 4, 5 and 7 in the future (a huge time saver). After step 1, just click the note and then click this palette item to insert the symbol and all you will have to do is reposition it.
Note 3: You can try adding this same symbol in the fingering text itself - between the two finger numbers - but this method leaves a gap between the two finger numbers and doesn't look nice to me.
Note 4: I have created and assigned one of the "User" text styles to this symbol. This could come in handy if I wanted to change something on all of those symbols, e.g. the color (my fingerings are in a custom color). If you want to do the same, do it as step 8) and before Note 2.
I'll be glad to see other answers - maybe there is a better way?

By the way, the aforementioned fingering activity is described by some as an "elision".