So many cool things in drum replacer. Some are not as well known.
 
1- Adding notes: Sometimes you set up the Filter and interval but don't want to tweak it just to catch a few notes.
Simply left click on the lower half of the Drum replacer timeline to add in a note.
 
2- Remove stray notes: As above, sometimes the filter or interval are set, but there's that one defunct note that's like 5 feet away from the real drum hit. Right click on the stem to remove it. Then add in a note using procedure/Step 1.
 
3- Add Velocity's: On custom notes you put in yourself (see Step 1) You can adjust these velocity's by clicking on the stem and holding( on custom note). A number will appear with the Velocity. Dragging up or down changes the value of the notes velocity.
 
4- Using a delayed hit: One can set up replacement hits to be a little early or a little late.
This works perfect on Snare hits. Hover your mouse over the Audio photo and click and hold, Drag right or left.
I find when Stacking drum, giving the second or third snare a little bit of delayed time thickens it up VS. leaving it in perfect time with the previous snare hit.

Treefight
This is VERY interesting to me - how does one can make an SFZ file with a multisampled instrument?

sfz files are text files that may be created and maintained using a text editor such as notepad or dedicated editors such as sfZed or SFZ Designer. In addition to the examples included with Drum Replacer, Session Drummer includes quite a few sfz files and samples that also work in Drum Replacer. There is also a tool written by Bill Jackson called CwDrSfzMaker available from the SONAR Resources and Utilities page to create sfz files from 3rd party drum synths.
 
 

Treefight
 And once placed in the Drum Replacer content library, what capabilities would you have within the Drum Replacer? 
 
For example, if that multisampled instrument contained a particular sample, for lack of a better work, of a snare hit, could that be loaded into the drum replacer as a Drum Replacement sound/element, i.e., to replace a recorded snare with a sample from the converted-then-imported sounds of the multisampled instrument?

yes

Y'all need a drummer buddy, Craig. They're really not such bad people.

Treefight
This is VERY interesting to me - how does one can make an SFZ file with a multisampled instrument?

I learned just about everything I know from one of Craig's articles in SOS
http://www.soundonsound.com/techniques/customising-sonars-sfz-files
 
There are also a few tools out there that can help in the process to speed up the monotonous steps.
Its very fun. I've made some incredible drum kits. Sampled from my own kit.