In Sibelius, the only choice I've found in this case is to increase the curvature of the tie/slur to avoid the time signature, which results in a fairly ridiculous-looking curve. I've tried using the "Erase background" function for the Time Signature text style, but it only erases the nearby barlines and leaves the curves intact.
A similar problem occurs when I'm writing a string part with harmonics and wish to insert an "actual sound" graphic in the same staff to the right of a tied note. The "solution" I came up with is to draw two unattached slurs and drag them in a drastic manner so as to make the middle endpoints appear to be part of the same curve. This wastes time and looks awful if the formatting changes even a little.
So, with high hopes, here's my suggestion:
Incorporate some sort of dialog that allows one to create an erasure box around specified objects. Its dimensions would be editable, much like those of the "Erase background" choice in the Border menu for Text Styles. • This erasure box could have a list of applicable objects to erase that could be checked or unchecked per the user's preference, such as erasing curves but not staff lines.
• Even better would be the ability to place different objects in different layers (like in Photoshop—or even, I believe, Noteworthy Composer!) which could go behind or in front of the erasure box. This would eliminate the need for a separate "objects to erase / not erase" dialog.
