diff --git a/backend/relations.md b/backend/relations.md
index e109d20e..fb8618f5 100644
--- a/backend/relations.md
+++ b/backend/relations.md
@@ -123,6 +123,9 @@ Option | Type | Description
 ------------- | ------------- | -------------
 `title` | Both | a popup title, can refer to a [localization string](../plugin/localization). <br/> Additionally, you can customize the title for each mode individually by setting this to an associative array, with the key being the mode and the value being the title used when displaying that mode. Eg: `form: acme.blog::lang.subcategory.FormTitle`.
 `context` | Form | context of the form being displayed. Can be a string or an array with keys: create, update.
+`size` | Both | the size of the popup used to manage records. Available sizes: `giant`, `huge`, `large`, `small`, `tiny`, `adaptive`. Default: `huge`
+`popupClass` | Both | custom CSS class(es) to apply to the popup used to manage records. Default: `null`
+`allowDismiss` | Both | allows the popup to be dismissed by clicking the backdrop area next to it. If the popup contains unsaved changes, it stays open, shakes and shows a warning flash message instead. Default: `false`
 
 ## Relationship types