This article goes over App-ID application Groups.

In Junos OS, application identification allows you to group applications in policies. Applications can be grouped under predefined and custom application groups. The entire predefined application group can be downloaded as part of the IDP or application identification security package. You can create custom application groups with a set of similar applications for consistent reuse when defining policies.

1- Can I edit existing pre-defined groups?

2- Can I create new groups?

https://www.juniper.net/documentation/us/en/software/junos/application-identification/topics/topic-map/security-application-identification-predefined-custom-application-groups.html

1- To customize a predefined application group, you must first disable the predefined group. Note that a disabled predefined application group remains disabled after an application database update (request services application-identification group disable). You can then use the operational command request services application-identification group to copy the disabled predefined application group. The copied group is placed in the configuration file, and the prefix “junos” is changed to “my”. At this point, you can modify the list of applications in “my” application group and rename the group with a unique name.

To reassign an application from one custom group to another, you must remove the application from its current custom application group, and then reassign it to the other.

2- To configure a custom application group for application identification:

Set the name of your custom application group.

[edit services application-identification]
user@host# set application-group my_web 

Add the list of applications that you want to include in your custom application group.

[edit services application-identification]
user@host# set application-group my_web applications junos:HTTP
user@host# set application-group my_web applications junos:FTP 
user@host# set application-group my_web applications junos:GOPHER 
user@host# set application-group my_web applications junos:AMAZON 

Set the name of a second custom application group.

[edit services application-identification]
user@host# set application-group my_peer 

Add the list of applications that you want to include in the group.

[edit services application-identification]
user@host# set application-group my_peer applications junos:BITTORRENT 
user@host# set application-group my_peer applications junos:BITTORRENT-APPLICATION 
user@host# set application-group my_peer applications junos:BITTORRENT-WEB-CLIENT