You can list all labels with corresponding ids like this (map0 is always added by default to first node, I added "kitchen" manually with set_label service):
$ sqlite3 rtabmap.db "select label, id from Node where label is not null order by label"
kitchen|7
map0|1
Based on the id, you can get the pose with:
$ rtabmap-report --poses rtabmap.db
$ cat rtabmap_slam.txt
#timestamp x y z qx qy qz qw id
0.042000 0.000004 0.000005 0.000000 0.000000 0.000000 -0.000000 1.000000 1
3.162000 0.458245 -0.001795 0.000000 0.000000 0.000000 -0.007404 0.999973 4
4.221000 1.496625 -0.031159 0.000000 0.000000 0.000000 -0.018981 0.999820 5
5.241000 2.435575 -0.066169 0.000000 0.000000 0.000000 -0.015919 0.999873 6
6.261000 2.585459 -0.070988 0.000000 0.000000 0.000000 -0.014342 0.999897 7
95.361000 2.811392 -0.078766 0.000000 0.000000 0.000000 -0.020893 0.999782 91
96.402000 3.734360 -0.147757 0.000000 0.000000 0.000000 -0.047059 0.998892 92
97.440000 4.168826 -0.180322 0.000000 0.000000 0.000000 -0.021443 0.999770 93