form:
  fields:
    tabs:
      fields:
        options:
          type: tab

          fields:

            sitemap:
              type: section
              title: Sitemap
              underline: true

              fields:
                header.sitemap.changefreq:
                  type: select
                  label: Sitemap change frequency
                  default: ''
                  options:
                    '': Use Global
                    always: Always
                    hourly: Hourly
                    daily: Daily
                    weekly: Weekly
                    monthly: Monthly
                    yearly: Yearly
                    never:  Never

                header.sitemap.priority:
                  type: select
                  label: Sitemap Priority
                  default: ''
                  options:
                    '': Use Global
                    '0.1': 0.1
                    '0.2': 0.2
                    '0.3': 0.3
                    '0.4': 0.4
                    '0.5': 0.5
                    '0.6': 0.6
                    '0.7': 0.7
                    '0.8': 0.8
                    '0.9': 0.9
                    '1.0': 1.0
                  validate:
                    type: float

form:
  fields:
    tabs:
      fields:
        options:
          type: tab

          fields:

            sitemap:
              type: section
              title: Sitemap
              underline: true

              fields:
                header.sitemap.changefreq:
                  type: select
                  label: Sitemap change frequency
                  default: ''
                  options:
                    '': Use Global
                    always: Always
                    hourly: Hourly
                    daily: Daily
                    weekly: Weekly
                    monthly: Monthly
                    yearly: Yearly
                    never:  Never

                header.sitemap.priority:
                  type: select
                  label: Sitemap Priority
                  default: ''
                  options:
                    '': Use Global
                    '0.1': 0.1
                    '0.2': 0.2
                    '0.3': 0.3
                    '0.4': 0.4
                    '0.5': 0.5
                    '0.6': 0.6
                    '0.7': 0.7
                    '0.8': 0.8
                    '0.9': 0.9
                    '1.0': 1.0
                  validate:
                    type: string

Save the value as string in normal mode, correctly load as string in expert mode
Save the value as string in normal mode, correctly load as string in expert mode
