Does SQL Server / T-SQL support line-continuation to break up long strings?
Thankfully there is support for line-continuation in T-SQL via the \ (backslash) character. Just place that at the end of of a line, right before the newline / carriage-return + line-feed, and the newline will be ignored.

For text strings, this behaves as follows:

PRINT 'Line1\
Line2';


returns (in the "Messages" tab):

Line1Line2


For binary / hex strings, this behaves as follows:

PRINT 0x1234\
5678;


returns (in the "Messages" tab):

0x12345678;




In order to format binary files (Assemblies, Certificates) into text hex-byte strings for use in SQL scripts, I wrote a command-line utility called BinaryFormatter that I have released as open-source on GitHub. Not only does it convert binary file into a text representation, but it also uses line-continuation to spread long VARBINARY literals across as many rows are needed, based on the specified number of character to use per each row. The result is something along the lines of:

4D5A09DE34F178313345A4\
00007F4E39782EFC48D842\
00000000


which I then copy and paste into my script, as shown in the {...} area below:

CREATE ASSEMBLY [AssemblyName]
FROM 0x\
{output from BinaryFormatter}
;


For additional details on this topic, please see my blog post: 
Line-Continuation in T-SQL