@Karina To achieve that is quite easy. Here is a short guide.

In your database, e.g. MySQL, MariaDB, or whatever database you are using, you have to insert the following data in the 'id'. 'uri_orig' and 'uri_rewrite' fields of your 'sys_seo_uri_rewrites' table as suggested by @Alex T⚜️ :

RECORDS TO INSERT:

Rewrite Rule #1:

id: 1

uri_orig: view-group-profile

uri_rewrite: g

Rewrite Rule #2:

id: 2

uri_orig: view-persons-profile

uri_rewrite: u

Rewrite Rule #3:

id: 3

uri_orig: view-organization-profile

uri_rewrite: o

Rewrite Rule #4:

id: 4

uri_orig: item

uri_rewrite: i

Rewrite Rule #5:

id: 5

uri_orig: view-post

uri_rewrite: p 

Rewrite Rule #6:

id: 6

uri_orig: view-discussion

uri_rewrite: d

Rewrite Rule #7:

id: 7

uri_orig: view-event-profile

uri_rewrite: e

HOW TO DO THAT?

Please backup your 'sys_seo_uri_rewrites' table: or database first.

Assuming that you are using phpMyAdmin as your database administration / management tool:

OPTION 1: USING THE INSERT TAB

Please open the 'sys_seo_uri_rewrites' table and click on the 'Insert' tab. 

Enter the data in the corresponding fields and click on 'Go' to store them.

Records you just inserted can be seen by checking the 'Browse' tab.

Note: You don't need to enter the 'id' value. The 'id' field is an auto-increment field, meaning the id will be generated automatically when a new record is inserted into the table. Just enter records (data) in sequence as shown above. But it's ok if you would like to enter it (the 'id' value) manually. There is no problem at all.

OPTION 2: RUNNING A DATABASE QUERY

A. SINGLE ROW INSERT (One by One):

Just run the following database query:

INSERT INTO `sys_seo_uri_rewrites` (`id`, `uri_orig`, `uri_rewrite`) VALUES (NULL, 'view-group-profile', 'g');

Please repeat this query for all the remaining Rewrite Rules listed above one by one (view-persons-profile, view-organization-profile etc) 

Same here, you don't need to enter the 'id' value as explained above.

Would you like to enter the id manually? Then, in the query, replace NULL with the 'id' value like this:

INSERT INTO `sys_seo_uri_rewrites` (`id`, `uri_orig`, `uri_rewrite`) VALUES ('1', 'view-group-profile', 'g');

B. MULTIPLE ROW INSERT (BEST OPTION):

To make your life easier and instead of inserting rows one by one, you can just insert them all in a single database query like this (my favorite option so far):

INSERT INTO `sys_seo_uri_rewrites` (`id`, `uri_orig`, `uri_rewrite`) VALUES
(1, 'view-group-profile', 'g'),
(2, 'view-persons-profile', 'u'),
(3, 'view-organization-profile', 'o'),
(4, 'item', 'i'),
(5, 'view-post', 'p'),
(6, 'view-discussion', 'd'),
(7, 'view-event-profile', 'e');

No matter which option you choose, If everything is done correctly, your 'sys_seo_uri_rewrites' table should look like the screenshot attached to this post.

All credit goes to @Alex T⚜️ and UNA Team:

https://unacms.com/cmts-view/1l129mt?sys=bx_forum&cmt_id=43455