diff --git a/src/environments/groupthm.pysty3 b/src/environments/groupthm.pysty3
index c47dee9..ce68af2 100644
--- a/src/environments/groupthm.pysty3
+++ b/src/environments/groupthm.pysty3
@@ -304,73 +304,82 @@ __HEADER__(Grouping theorems for easier customization.)
   }
 }
 
-% evname, star?
-\cs_new:Npn \declare_theorem_variants_aux:nn #1 #2
+\cs_new:Npn \add_theorem_to_group:n #1
+{
+  \clist_put_left:Nn \l_groupthm_groups_clist { #1 }
+}
+
+\NewDocumentCommand { \AddTheoremToGroup } { m }
+{
+  \add_theorem_to_group:n { #1 }
+}
+
+\cs_new:Npn \__new_theorem_variant_parser_aux:nnnn #1 #2 #3 #4
 {
   \exp_args:Nx\NewDocumentEnvironment
   {
-    #1\IfBooleanT{#2}{*}
+    #1\IfBooleanT{#4}{*}
   }
-  { !s !t+ }
+  {#2}
   {
     \clist_clear:N \l_groupthm_groups_clist
-    \IfBooleanT{##2}
+
+    #3
+
+    \IfBooleanT{#4}
     {
-      \clist_put_left:Nn \l_groupthm_groups_clist { dagger  }
-    }
-    \IfBooleanT{##1}
-    {
-      \clist_put_left:Nn \l_groupthm_groups_clist { star    }
-    }
-    \IfBooleanT{#2}
-    {
-      \clist_put_left:Nn \l_groupthm_groups_clist { starred }
+      \add_theorem_to_group:n { starred }
     }
     \__sort_group_names:
     \begin{__#1__groups_\clist_use:Nn \l_groupthm_groups_clist{_}}
   }
   {
     \clist_clear:N \l_groupthm_groups_clist
-    \IfBooleanT{##1}
+
+    #3
+
+    \IfBooleanT{#4}
     {
-      \clist_put_left:Nn \l_groupthm_groups_clist { star   }
-    }
-    \IfBooleanT{##2}
-    {
-      \clist_put_left:Nn \l_groupthm_groups_clist { dagger }
-    }
-    \IfBooleanT{#2}
-    {
-      \clist_put_left:Nn \l_groupthm_groups_clist { starred }
+      \add_theorem_to_group:n { starred }
     }
     \__sort_group_names:
     \end{__#1__groups_\clist_use:Nn \l_groupthm_groups_clist{_}}
   }
 }
 
+% envname, signature, definition
 \cs_new:Npn \new_theorem_variant_parser:nnn #1 #2 #3
 {
-  \NewDocumentEnvironment{#1}{#2}
-  {
-    \clist_clear:N \l_groupthm_groups_clist
-    #3
-    \__sort_group_names:
-    \begin{__#1__groups_\clist_use:Nn \l_groupthm_groups_clist{_}}
-  }
-  {
-    \clist_clear:N \l_groupthm_groups_clist
-    #3
-    \__sort_group_names:
-    \end{__#1__groups_\clist_use:Nn \l_groupthm_groups_clist{_}}
-  }
+  \__new_theorem_variant_parser_aux:nnnn { #1 } { #2 } { #3 } { \BooleanTrue }
+  \__new_theorem_variant_parser_aux:nnnn { #1 } { #2 } { #3 } { \BooleanFalse }
 }
+\cs_generate_variant:Nn \new_theorem_variant_parser:nnn { x n n }
 
 % envname, name, thmtools
 \cs_new:Npn \declare_theorem_variants:nnn #1 #2 #3 
 {
   \generate_theorem_variants:nnnn { #1 } { #2 } { #3 } { star, dagger, starred }
-  \declare_theorem_variants_aux:nn { #1 } { \BooleanTrue }
-  \declare_theorem_variants_aux:nn { #1 } { \BooleanFalse }
+  \declare_theorem_variants_aux:n { #1 }
+}
+
+% evname, star?
+\cs_new:Npn \declare_theorem_variants_aux:n #1
+{
+  \new_theorem_variant_parser:xnn
+  {
+    #1
+  }
+  { !s !t+ }
+  {
+    \IfBooleanT{##2}
+    {
+      \add_theorem_to_group:n { dagger }
+    }
+    \IfBooleanT{##1}
+    {
+      \add_theorem_to_group:n { star }
+    }
+  }
 }
 
 % envname, group-determining function