The solution was prescribed by @cayce :
A) Within the “Qubes Manager” GUI, I select/highlight the base template used for the AppVM/DispVM & click the “Settings” button
B) Within “Settings”, select the “Applications” tab & click the “Refresh applications” button
C) Upon seeing our expected application launcher, click “OK” button
D) Back in “Qubes Manager”, highlight the derivative AppVM & click the “Settings” button
E) Within “Settings”, select the “Applications” tab & we want to remove all “Selected” applications by clicking the “<<” button followed by clicking the “Apply” button
F) Next, navigate to the “Advanced” tab by clicking on it
G) Within the “Advanced” tab, de-select the “Disposable template” radio-box & click the “Apply” button
H) Remaining within the “Advanced” tab, re-select the “Disposable template” radio-box, click the “Apply” button
I) Still remaining within the “Advanced” tab, click the drop-down for “Default disposable template”, select the AppVM (same one we are currently configuring) and click the “Apply” button
J) Then, navigate back to the “Applications” tab by clicking on it
K) Within the “Applications” tab, highlight the desired application under “Available” (left-hand side) and click the “>” button to move the “Selected” (left-hand side), click the “Apply” button followed by the “OK” button
L) Finally, close the “Qubes Manager” GUI (your main menu of the “Application Launcher” ought refresh) & either navigate to or, search for your application.
If also using a derived “Named” DispVM, the application shortcut selection ought be inherited.
Thank @cayce and all of you very much for your time!