diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -15,6 +15,7 @@ specifiers:
   d3: ^7.8.4
   debug: ^4.3.4
   fpsmeter: ^0.3.1
+  immutable: ^4.3.0
   knockout: ^3.5.1
   lit: ^2.7.4
   n3: ^1.16.4
@@ -44,6 +45,7 @@ dependencies:
   d3: 7.8.4
   debug: 4.3.4
   fpsmeter: 0.3.1
+  immutable: 4.3.0
   knockout: 3.5.1
   lit: 2.7.4
   n3: 1.16.4
@@ -1156,6 +1158,10 @@ packages:
     resolution: {integrity: sha512-dcyqhDvX1C46lXZcVqCpK+FtMRQVdIMN6/Df5js2zouUsqG7I6sFxitIC+7KYK29KdXOLHdu9zL4sFnoVQnqaA==}
     dev: false
 
+  /immutable/4.3.0:
+    resolution: {integrity: sha512-0AOCmOip+xgJwEVTQj1EfiDDOkPmuyllDuTuEX+DDXUgapLAsBIfkg3sxCYyCEA8mQqZrrxPUGjcOQ2JS3WLkg==}
+    dev: false
+
   /internmap/2.0.3:
     resolution: {integrity: sha512-5Hh7Y1wQbvY5ooGgPbDaL5iYLAPzMTUrjMulskHLH6wnv/A+1q5rgEaiuqEjB+oxGXIVZs1FF+R/KPN3ZSQYYg==}
     engines: {node: '>=12'}