Using complex route Razor Page routing conventions that involve multiple variables in paths - url-rewriting

Question

Background
.NetCore 2 web application targetting the full .Net framework. We are moving from the conventional MVC separate Controller/View structure where we configured route rules using [Route()]/Get() attributes to handle routing to Razor Pages.
So far
Following the MS docs (https://learn.microsoft.com/en-us/aspnet/core/mvc/razor-pages/razor-pages-convention-features#page-model-action-conventions) I have the first tier of folders with a category ID being passed to the page;
e.g. '/category/15032/dashboard/' resolves to the page 'pages/category/dashboard'
`options.Conventions
.AddFolderRouteModelConvention("/category", model =>
{
int selectorCount = model.Selectors.Count;
for (int i = 0; i < selectorCount; i++)
{
SelectorModel selector = model.Selectors[i];
string[] segments = selector.AttributeRouteModel.Template.Split('/');
model.Selectors.Add(new SelectorModel
{
AttributeRouteModel = new AttributeRouteModel
{
Order = 1,
Template = AttributeRouteModel.CombineTemplates($"category/{{categoryid}}/{segments[1].ToLower()}", "{categoryPageTemplate?}")
}
});
}
});`
This works as expected. However, the problems arise when I try to add further depth to the folder structure.
The problem
Each category contains a sub-category, and then within that, an item. For example, I will include a deeply nested page.
e.g. '/category/15032/subcategory/543/item/211/status' should resolve to the page 'pages/category/subcategory/item/status'
The hope was that adding the following convention would handle this;
`options.Conventions
.AddFolderRouteModelConvention("/category/subcategory/item", model =>
{
int selectorCount = model.Selectors.Count;
for (int i = 0; i < selectorCount; i++)
{
SelectorModel selector = model.Selectors[i];
string[] segments = selector.AttributeRouteModel.Template.Split('/');
model.Selectors.Add(new SelectorModel
{
AttributeRouteModel = new AttributeRouteModel
{
Order = 1,
Template = AttributeRouteModel.CombineTemplates($"category/{{categoryid}}/subcategory/{{subcategoryid}}/item/{{itemid}}/{segments[2].ToLower()}",
"{itemPageTemplate?}")
}
});
}
});`
Error
Microsoft.AspNetCore.Routing.RouteCreationException: The following
errors occurred with attribute routing information:
For action: 'Page: /category/subcategory/item/dashboard' Error: The
route parameter name 'categoryid' appears more than one time in the
route template. Parameter name: routeTemplate
at
Microsoft.AspNetCore.Mvc.Internal.AttributeRoute.GetRouteInfos(IReadOnlyList
1 actions) at
Microsoft.AspNetCore.Mvc.Internal.AttributeRoute.AddEntries(TreeRouteBuilder
builder, ActionDescriptorCollection actions) at
Microsoft.AspNetCore.Mvc.Internal.AttributeRoute.GetTreeRouter() at
Microsoft.AspNetCore.Mvc.Internal.AttributeRoute.RouteAsync(RouteContext
context) at
Microsoft.AspNetCore.Routing.RouteCollection.d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown --- at
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
task) at
Microsoft.AspNetCore.Builder.RouterMiddleware.d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown --- at
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
task) at
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.d__7.MoveNext()
Question
Note: the folders are nested like this because there are quite a few pages to the site, so keeping things organised is quite important.
How can I avoid this error? Do I have to change the URL structure - this has proven fairly readable (don't normally use ID numbers)? Does anyone have any examples of a similar nested structure (I have had difficulty in finding examples)?