Steps to reproduce:
- create Welcome sample project
- do step into
- open Variables
- call "Visible columns" dialog and enable Type column, Type column appears in the table
- press "Show Watches inside Variables view" button
Result: Type column disappears from Variables table. It fact "Show Watches inside Variables view" button resets all columns which were added during the debug session e.g. if we had only Name column when started debug session then Name remains after clicking the button.

Debugger console shows:
~"GNU gdb 6.8-debian\n"
~"Copyright (C) 2008 Free Software Foundation, Inc.\n"
~"License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>\n"
~"This is free software: you are free to change and redistribute it.\n"
~"There is NO WARRANTY, to the extent permitted by law.  Type \"show copying\"\n"
~"and \"show warranty\" for details.\n"
~"This GDB was configured as \"i486-linux-gnu\".\n"
&"/home/ap153252/.gdbinit: No such file or directory.\n"
(gdb) 
2-gdb-set print repeat 0
3-gdb-set backtrace limit 1024
4-file-exec-and-symbols  "/home/ap153252/NetBeansProjects/Welcome_36/dist/Debug/GNU-Linux-x86/welcome_36"
2^done
(gdb) 
3^done
(gdb) 
4^done
(gdb) 
5-file-list-exec-source-file
6cd /home/ap153252/NetBeansProjects/Welcome_36
7-exec-arguments "arg 1" "arg 2" "arg 3" "arg 4"
8-gdb-set environment OMP_NUM_THREADS=2
5^done,line="26",file="welcome.cc",fullname="/home/ap153252/NetBeansProjects/Welcome_36/welcome.cc",macro-info="0"
(gdb) 
9-break-insert -t main
10-exec-run
11info proc
&"cd /home/ap153252/NetBeansProjects/Welcome_36\n"
~"Working directory /home/ap153252/NetBeansProjects/Welcome_36.\n"
6^done
(gdb) 
7^done
(gdb) 
8^done
(gdb) 
9^done,bkpt={number="1",type="breakpoint",disp="del",enabled="y",addr="0x08048765",func="main",file="welcome.cc",fullname="/home/ap153252/NetBeansProjects/Welcome_36/welcome.cc",line="35",times="0"}
(gdb) 
10^running
(gdb) 
10*stopped,thread-id="0",frame={addr="0x08048765",func="main",args=[{name="argc",value="5"},{name="argv",value="0xbf867614"}],file="welcome.cc",fullname="/home/ap153252/NetBeansProjects/Welcome_36/welcome.cc",line="35"}
(gdb) 
&"info proc\n"
~"process 18521\n"
~"cmdline = '/home/ap153252/NetBeansProjects/Welcome_36/dist/Debug/GNU-Linux-x86/welcome_36'\n"
~"cwd = '/home/ap153252/NetBeansProjects/Welcome_36'\n"
~"exe = '/home/ap153252/NetBeansProjects/Welcome_36/dist/Debug/GNU-Linux-x86/welcome_36'\n"
11^done
(gdb) 
12-stack-list-frames
12^done,stack=[frame={level="0",addr="0x08048765",func="main",file="welcome.cc",fullname="/home/ap153252/NetBeansProjects/Welcome_36/welcome.cc",line="35"}]
(gdb) 
13-stack-list-arguments 1
14-var-update * 
13^done,stack-args=[frame={level="0",args=[{name="argc",value="5"},{name="argv",value="0xbf867614"}]}]
(gdb) 
15-stack-list-locals --simple-values
14^done,changelist=[]
(gdb) 
15^done,locals=[{name="i",type="int",value="134514793"}]
(gdb) 
16-var-create - * i
17-var-create - * argc
16^done,name="var1",numchild="0",value="134514793",type="int"
(gdb) 
18-var-create - * argv
19-var-update * 
17^done,name="var2",numchild="0",value="5",type="int"
(gdb) 
20-var-show-attributes var1
21-var-show-attributes var2
18^done,name="var3",numchild="1",value="0xbf867614",type="char **"
(gdb) 
19^done,changelist=[]
(gdb) 
22-var-show-attributes var3
20^done,attr="editable"
(gdb) 
21^done,attr="editable"
(gdb) 
23-var-evaluate-expression var1
24-var-evaluate-expression var2
22^done,attr="editable"
(gdb) 
25-var-evaluate-expression var3
23^done,value="134514793"
(gdb) 
24^done,value="5"
(gdb) 
25^done,value="0xbf867614"
(gdb) 
26-stack-list-locals --simple-values
26^done,locals=[{name="i",type="int",value="134514793"}]
(gdb)