Making Sostenudo Marks


The line is from the list of staff lines in the lines dialog and is called "vertical bracket (left)". It comes after the five types of pedal line.
 
Positioning it is difficult. It's like trying to use the arpeggio line. Pressing Alt+Right moves you through the three points, but in this case they are the top, middle and bottom, instead of the left, middle and right. You can extend the line up or down with keystrokes by selecting the left and right end with Alt+Left/Right. Then use Ctrl+Up/Down or Up/Down for small increments. Just remember that the left end is the top and right end is the bottom.
 
You can see what the X and Y coordinates of the top of the line are by looking at the X and Y boxes in the general panel of the properties window. The coordinates for the bottom are the X and Y coordinates in the lines panel.
 
The top and bottom of the line both have a small "hook" which is really a short horizontal line pointing to the right. The bottom hook needs to be just below the bottom note, and the top hook, just above the top note.
 
Since you have a little sight, you may be able to do this without all the number crunching, but it is possible to work out what numbers you should give the Y coordinates for the bottom and top of the line.
 
You can work this out by the numbers. The middle line of the staff has a Y coordinate of 0, this corresponds to D3 with the bass clef. Each line is 1 space away from the middle of the staff, and C2 is 4 lines below D3. This gives Y = -4. You also need to put the line just below the bottom of the note head, which extends for 0.5 spaces above and below the line. This gives you a total of -4.5. You should also add a small clearance below the note as well.
 
I see in the score that the Y coordinate is actually -4.63, which sounds about right. This number comes from 4 spaces between the centre line and the centre of the note head + half of the note head + a few fractions of a space for clearance.
 
The top of the line is more complicated because it needs to be on the staff above and there is no absolute way to  work out how far apart the staves are. In theory, the gap between staves option in the engraving rules dialog should tell you how far apart staves are, but only if they haven't been moved or justified. In this score the gap is 5.5 spaces. This means that the bottom line of the top staff is 5.5 spaces above the top line of the bottom staff. This in turn means that the middle line of the top staff is 9.5 spaces above the middle line of the bottom staff. You can now calculate where the top of the line needs to be from the middle line of the bottom staff.
 
D4 is 2.5 spaces from the middle line of the top staff, so it's Y coordinate from the the middle of the bottom staff is 9.5 - 2.5 = 7. This refers to the middle of the note, so the top of the note is 7.5 spaces away. Adding a little for clearance puts it at 7.63.
 
Unfortunately, the Y coordinate for the top of the line is actually 10. This suggests that either the staves are more than 5.5 spaces apart, or that the line stops several spaces above the note. Given that some of the notes in the right hand are very low for a treble clef (E3), I think it likely that the staves have been dragged apart, however, I have no way of telling which without sighted assistance.
 
As I said, this is not easy, and there's a lot of guess work involved.