Add clarity to ProcessTemplate fields section to make it clear that you have to save newly added fields before they become editable in context. Also add note about how to drag to adjust column width of individual fields.

wire/core/Config.php

@@ -132,7 +132,7 @@
  * @property string $moduleServiceURL URL where the modules web service can be accessed #pw-group-modules
  * @property string $moduleServiceKey API key for modules web service #pw-group-modules
  * @property bool $moduleCompile Allow use of compiled modules? #pw-group-modules
- * @property array $wireMail Default WireMail module settings. #pw-group-modules
+ * @property array $wireMail Default WireMail module settings. See /wire/config.php $config->wireMail for details. #pw-group-system
  * @property array $moduleInstall Admin module install options you allow. #pw-group-modules
  * 
  * @property array $substituteModules Associative array with names of substitute modules for when requested module doesn't exist #pw-group-modules
@@ -168,6 +168,7 @@
  * @property array $statusFiles File inclusions for ProcessWire’s runtime statuses/states. #pw-group-system @since 3.0.142
  * @property int $status Value of current system status/state corresponding to ProcessWire::status* constants. #pw-internal
  * @property null|bool $disableUnknownMethodException Disable the “Method does not exist or is not callable in this context” exception. (default=null) #pw-internal
+ * @property string|null $phpMailAdditionalParams Additional params to pass to PHP’s mail() function (when used), see $additional_params argument at https://www.php.net/manual/en/function.mail.php #pw-group-system
  * 
  * @property int $rootPageID Page ID of homepage (usually 1) #pw-group-system-IDs
  * @property int $adminRootPageID Page ID of admin root page #pw-group-system-IDs

wire/core/FieldSelectorInfo.php

@@ -111,6 +111,7 @@ class FieldSelectorInfo extends Wire {
 
 			// skip over native properties that aren't used in selectors
 			if(in_array($name, array('pages_id', 'keys', 'xtra', 'sort'))) continue; 
+			if(!is_string($schemaType)) continue;
 
 			if($name == 'data') {
 				// base property

wire/modules/Process/ProcessTemplate/ProcessTemplate.css

@@ -42,6 +42,14 @@ input[disabled=disabled] {
 	margin-right: 0.5em; 
 }
 
+#wrap_fieldgroup_fields .notes {
+	display: none;
+}
+#wrap_fieldgroup_fields.field-added .notes {
+	display: block;
+}
+
+
 /**
  * Import/export 
  *

wire/modules/Process/ProcessTemplate/ProcessTemplate.js

@@ -351,6 +351,7 @@ function ProcessTemplateAsmSelect() {
 			// eventData is provided by a change event triggered from asmSelect plugin after a sort or select event
 			if(typeof eventData == "undefined") return;
 			if(typeof eventData.type == "undefined") return;
+			if(eventData.type === 'add') $inputfield.addClass('field-added'); 
 			if(eventData.type != 'sort') return;
 
 			// update row identifications after any changes

wire/modules/Process/ProcessTemplate/ProcessTemplate.module

@@ -1018,7 +1018,13 @@ class ProcessTemplate extends Process implements ConfigurableModule {
 		if($forField) {
 			$select->description = sprintf($this->_('Define the custom fields for “%s”. It is not necessary to configure anything else here.'), $forField->name);
 		} else {
-			$select->description = $this->_('Define the fields that are used by this template. You may also drag and drop fields to the desired order or [create a new field](../field/add).'); // Fields definition, description
+			$select->description = 
+				$this->_('Select the fields that are used by this template and drag/drop to the desired order.') . ' ' . 
+				sprintf(
+					$this->_('You may also click field name or label to edit in the context of this template, click/drag the percent indicator to adjust width, or [create a new field](%s).'),
+					'../field/add'
+				);
+			$select->notes = $this->_('Save this template to make newly added fields editable here.'); 
 		}
 		$select->icon = 'cube';
 		$select->attr('name', 'fieldgroup_fields');